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From Piotr Nowojski <pi...@data-artisans.com>
Subject Re: [flink-cep] Flick CEP support for the group By operator
Date Fri, 23 Nov 2018 15:32:29 GMT
Hi,

Yes, sure. Just use CEP on top of KeyedStream. Take a look at `keyBy`:

https://ci.apache.org/projects/flink/flink-docs-release-1.6/dev/stream/operators/

Piotrek 

> On 23 Nov 2018, at 16:04, Spico Florin <spicoflorin@gmail.com> wrote:
> 
> Hello!
> 
> I'm using Flink 1.4.2 and I would like to use a group by operator based on value of my
event stream. The functionality that I would like to achieve is similar to the following Esper
EPL
> (excerpt http://esper.espertech.com/release-5.2.0/esper-reference/html/epl_clauses.html#epl-grouping-aggregating
<http://esper.espertech.com/release-5.2.0/esper-reference/html/epl_clauses.html#epl-grouping-aggregating>)
> 
> 
> select symbol, tickDataFeed, median(volume) 
> from StockTickEvent.win:time(30 sec) 
> group by symbol, tickDataFeed
>  <>
> 
> So, does the Flick CEP  support such a group by functionality? 
> 
> If yes what is syntax?
> 
> 
> 
> I look forward for your answers.
> 
> 
> 
> Best regards,
> 
>  Florin 
> 
> 
> 
> 
> 
> (excerpt http://esper.espertech.com/release-5.2.0/esper-reference/html/epl_clauses.html#epl-grouping-aggregating
<http://esper.espertech.com/release-5.2.0/esper-reference/html/epl_clauses.html#epl-grouping-aggregating>)
> "You can list more then one expression in the group by clause to nest groups. Once the
sets are established with group by the aggregation functions are applied. This statement posts
the median volume for all stock tick events in the last 30 seconds per symbol and tick data
feed. Esper posts one event for each group to statement listeners:
> In the statement above the event properties in the select list (symbol, tickDataFeed)
are also listed in the group by clause. The statement thus follows the SQL standard which
prescribes that non-aggregated event properties in the select list must match the group by
columns."
> 


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